1. The Field of the Invention
The present invention relates to apparatus and methods for the dose-to-effect transmucosal administration of medicaments. More particularly, the present invention is directed to an adjustable apparatus and methods for noninvasive administration of precise amounts of medicaments through mucosal tissues by direct medicament contact to mucosal tissues.
2. The Background of the Invention
Recently, numerous advancements have taken place in the field of pharmacology an pharmaceutics with respect to the administration of drugs to treat various conditions. Despite the tremendous advancements in the field, however, drugs continue to be administered using substantially the same techniques that have been used for many decades. The vast majority of pharmaceutical agents continue to be administered either orally or by injection. Nevertheless, it is frequently found in the art that neither of these administration routes are effective in all cases, and both administration routes suffer from several disadvantages.
Oral administration is probably the most prevalent method of administering pharmacological medicaments. The medicament is generally incorporated into a tablet, capsule, or a liquid base, and then swallowed. The oral administration modality is often preferred because of its convenience. In addition, oral administration is generally nonthreatening, painless, and simple to accomplish for most patients.
Nevertheless, oral administration of drugs suffers from several disadvantages. One disadvantage is that pediatric and geriatric patients frequently have difficulty swallowing pills and other solid dosage forms, and such patients often refuse to cooperate in swallowing a liquid medication. In addition, for many medicaments, the act of swallowing the medicament often requires fluids and increases gastric volume and the likelihood of nausea and vomiting.
A further problem with oral administration is that the rate of absorption of the drug into the bloodstream after swallowing varies from patient to patient. The absorption of the drug is dependent upon the movement of the drug from the stomach to the small and large intestines, the effects of secretions from these organs, and on the resulting pH within the stomach and intestines. Anxiety and stress can dramatically reduce these movements and secretions, prevent or reduce the final effects of the drug, and delay onset of the drug's effects.
Most significant is the fact that there is normally a substantial delay between the time of oral administration and the time that the therapeutic effect of the drug begins. As mentioned above, the drug must pass through the gastrointestinal system in order to enter the bloodstream; this typically takes forty-five minutes or longer. As mentioned above, anxiety and stress often increase this delay. For many applications where immediate relief from pain or a serious medical condition or immediate effectiveness of the drug is required, this delay is unacceptable.
An additional disadvantage of oral administration is that many important therapeutic peptides and proteins are deactivated by the strong acidic environment and proteolytic enzymes in the gastrointestinal tract. Other drugs which are absorbed into the blood stream are almost immediately metabolized because the veins from the stomach and the small and large intestines pass directly through the liver. Thus, drugs entering the bloodstream must first pass through the liver before distribution into the general blood circulation. More than sixty percent of most drugs (and essentially one hundred percent of certain drugs) are removed from the patient's bloodstream during this "first pass" through the liver. The result is that oral administration is impractical for many drugs.
Further, additional stress is placed on the liver as it removes the excess drug from the bloodstream. This is particularly severe if the drug treatment has been occurring over an extended period of time. The liver may become overloaded with the drug's metabolite which then must be excreted. As a result, there is an increased risk of hepatic or renal disorders.
Another difficulty encountered in administering drugs orally is that dosages are prepared or determined for use with an "average" patient. Most drugs have widely varying effects on different patients. These effects depend upon patient habits, subtle genetic differences between patients, blood volumes, age, and numerous other known and unknown factors. Introducing a bolus of drug orally does not provide the ability to control the precise dose needed to obtain the desired effect, rather the dose is estimated in order to produce an average effect in an average patient. The result may be underdosing or overdosing a particular patient.
Underdosing a patient because of a low susceptibility to the drug fails to evoke the response sought by the physician. Overdosing the patient may dangerously affect vital body functions. Both underdosing and overdosing should be avoided.
In order to avoid some of the disadvantages of oral administration, injection is frequently used. Injecting a drug (generally intravenously or intramuscularly), results in rapid entry of the drug into the patient's bloodstream. In addition, this type of delivery avoids the removal of large quantities of the drug by the patient's liver. As a result, less total drug is usually needed compared to orally administered drugs. The drug instead becomes rapidly distributed to various portions of the patient's body before exposure to the liver.
Most patients, particularly children and geriatric adults, have an aversion to injections. In some patients, this aversion may be so pronounced as to make the use of injections a serious concern. Since intense psychological stress can exacerbate a patient's debilitated condition, it sometimes becomes undesirable to use injections where the patient is seriously ill or suffers from a debilitating condition or injury.
In addition, individual variations in susceptibility in the metabolism of various drugs (particularly drugs with central nervous system activity) are even more profound when utilizing the injection route. In many instances to prevent overdosing, it is the practice to inject a patient with a lower than average dose and then supplement the dose with additional injections as necessary. This "titration" makes necessary the use of repeated injections, which in turn greatly increases stress on the patient. Again, a precise dose cannot be administered to produce a precise effect because the patient's response varies widely depending on the specific characteristics of the specific patient.
Some investigators have suggested that it may be possible to administer medication through the buccal mucosa of the cheek pouch or by sublingual administration. See, U.S. Pat. No. 4,671,953 entitled "METHODS AND COMPOSITIONS FOR NONINVASIVE ADMINISTRATION OF SEDATIVES, ANALGESICS, AND ANESTHETICS." Such administration through the mucosal tissues of the mouth, pharynx, and esophagus of therapeutic drugs possesses a distinct usefulness. Administration of drugs by this route does not expose the drug to the gastric and intestinal digestive juices. In addition, the drugs largely bypass the liver on the first pass through the body, thereby avoiding additional metabolism and/or inactivation of the drug
Generally the drugs which are administered by any of the methods described above have an unpleasant taste. As a result, in order to allow for buccal or sublingual administration through the oral mucosal tissues the drug is typically incorporated into some type of pleasant tasting mass, such as a "candy" matrix.
In the manufacture of conventional medicated candy products, the therapeutic agent is added to a molten candy mass. The resultant mixture is then thoroughly mixed to ensure proper distribution of the drug within the molten candy mass. The molten mixture is then poured into a mold cavity of desired size and shape and allowed to solidify into a solid mass.
For effective application of the drug, the final candy matrix may contain the drug uniformly distributed throughout in order to ensure uniform levels of medication. Alternatively, for some applications, varying concentrations within known and controlled ranges may be desired to vary the rate of drug administration. Difficulties are encountered in attempting to blend solid drugs in a uniform or otherwise carefully controlled manner. Many drugs are insoluble, or only partially soluble, in one or more of the ingredients of the hard candy base. Thus, the resultant product is often found to be lacking in uniform or controlled distribution of the drug.
In addition, it is often found that at the high temperatures needed to melt and form the candy mass, considerable decomposition of the medicament takes place. While the extent of decomposition may vary, high temperatures are generally undesirable in the handling and processing of medications. Thus, the formation process of prior art candy matrixes may itself degrade and/or inactivate the therapeutic agent.
Furthermore, many presently available medicated candy lozenges tend to crumble when placed in the mouth. As a result, uniform release of the drug into the mucosal tissues does not take place. Rather, the crumbled lozenge is mostly chewed, and swallowed, and the drug enters the bloodstream through the stomach and intestines as described above. Thus, it will be appreciated that candy lozenges have very definite limitations for use in the administration of a drug through the oral mucosal tissues. As a result, lozenges have not been used to administer potent, fast-acting drugs, such as drugs that affect the central nervous system, the respiratory system, the cardiovascular system, the renal vascular system, or other similar body systems.
While the administration of certain drugs through the oral mucosal tissues has shown promise, development of a fully acceptable method for producing a medication in a desirable form and administering the medication has been elusive. It has not been possible to develop an acceptable candy product for use with most drugs without heating the product to the point where degradation will be expected.
It should also be noted that pH conditions within the mouth may tend to adversely affect the administration of certain lipophilic and nonlipophilic drugs by the mucosal administration route. It has been found in the art that administration of drugs through the mucosal tissues generally occurs best when the drug is in the unionized form. Variations in pH affect the percentage of the drug which is unionized at a particular point in time. As a result, the pH conditions within the mouth can limit the effectiveness of certain drugs administered buccally or sublingually in that those conditions cause the drug to exist in the ionized form which is largely unavailable for transfer across the mucosal tissues.
Other medicaments are substantially nonlipophilic and do not naturally permeate mucosal tissues. Many important drugs, such as protein and peptide drugs having very large molecular weights and electrically charged functional groups, do not naturally permeate mucosal tissues. For example, insulin is a drug which must be administered intravenously, intramuscularly, or subcutaneously because it may not be administered orally without deactivation by the digestive system. In addition, insulin does not readily permeate mucosal tissues. Hence it would be a significant advancement in the art of drug administration to provide suitable apparatus and methods permitting the noninvasive, transmucosal administration of drugs which do not naturally permeate mucosal tissues and which are not suitable for oral administration.
It would be another important advancement in the art of administering medicaments, to provide apparatus and methods which deliver the precise dosage of the medicament to achieve a precise effect in every patient. A related advancement in the art would be to provide such apparatus and methods that avoid the disadvantages of overdosing, underdosing, and the immediate metabolism or inactivation of the digestive system, yet do not involve injection by needle into the patient.
It would also be an important advancement in the art to provide apparatus and methods for administering medicaments which do not subject the medicament to decomposition temperatures.
Such apparatus and methods of manufacture are disclosed and claimed herein.